Versioning for init script

[Ryan Clancy]

In order to have re-producible results, we need to ensure that the version (be it a commit id, version string, etc.) is passed to the init script. In the images currently, artifacts are downloaded at a fixed version hard-coded into the script or are checking out the latest code from a git repo and building from source.

Much like init and search, we should pass a JSON string to the init script with a version string field.